maybe it's because I'm on a college campus and go into coffee shops to buy drinks pretty regularly and everybody there is studying, but I don't see the problem with it. I've never done it personally. But people sitting in there do not affect the foot traffic that's the majority of the costumers that walk in the store, buy coffee real quick, then rush back out. Coffee shops are not sit down restaurants. I highly doubt a coffee shop will lose costumers if all the chairs are filled than if no chairs were filled. People would still buy their coffee, but instead of sitting around like everybody else in there, if the chairs are full then they'll just buy their coffee and take it with them (store still makes same profit).
I can completely understand a restaurant doing this. Customers need chairs, more empty chairs means a faster rotation of customers and a higher profit. But coffee shops don't have the same kind of customers. If everybody is minding their own business in there, I don't see whats wrong with someone on their laptop or reading a book. The store is smart enough to know that by offering wireless internet, they are encouraging people to linger, why else offer it?
I personally study sitting right here, but if going to a coffee shop that's a 2 minute walk from here will help me study faster or read a book quicker that I need to read for my class, then whynot go? It'll at least prevent me from getting on getbig and posting while I'm studying, maybe meet someone with the same interests, motivate me to study harder when I see other people also studying, and not to mention the coffee